This invention relates to a precombustion chamber construction for a diesel engine, and more particularly a construction having thermal insulating or adiabatic spaces about a ceramic precombustion chamber for a diesel engine.
Ceramic precombustion chambers for diesel engines have been practically used because of their superiority in heat resistance and thermal insulation. Such ceramic precombustion chambers have been disclosed in Japanese Utility Model Application Laid-open Nos. 58-27,526, 58-175,118, and 59-21,024. Referring to FIG. 1, in conventional precombustion chambers, the ceramic precombustion chamber 1 comprises a thermal insulating space 13 provided between an outer circumference of the ceramic precombustion chamber 8 and an inner circumference of a metal cylinder head 2, and a glow-plug receiving aperture 7 in an upper portion of the chamber 8 for fitting a glow-plug 14.
In such a precombustion chamber for an internal combustion engine, the glow-plug is often provided on a side of a side wall of the ceramic precombustion chamber by reason of design. In this case, however, there is a clearance 7 between the glow-plug and the glow plug receiving aperture, through which burned gases leak into the thermal insulating space to lower the thermal insulating effect. Moreover, actual compression ratios of the engine are changed to interfere with normal engine performance.